Metallic coating systems are used in many situations where a metal substrate is subjected to extreme conditions such as high temperature, oxidation and corrosion producing atmospheres and the like. Metallic coating systems are particularly used in high pressure turbine applications to protect the airfoils from the aggressive combustion environment. These coatings are used to shelter components from hot corrosion and/or oxidation attack experienced by the components in these severe conditions.
Physical vapor deposition applications of metallic bond coatings permit deposition of specific chemistries in localized areas to provide the necessary environmental protection. These coatings are used as a stand-alone coating or as a bond coat for a thermal barrier ceramic topcoat.
Two major classes of metallic coatings conventionally used as protective systems against hot corrosion or oxidation of Ni-base superalloys are diffusion aluminides and overlay coatings. One family of overlay metallic coatings is described in commonly owned U.S. Pat. No. 6,919,042. These coatings include various elements added to nickel and have been found to be useful in some applications. As combustion engine technology development continues, the components are subjected to ever more corrosive and/or oxidizing attack, thus, design and implementation of coating systems with enhanced application specific capabilities (e.g., protecting against high temperature oxidation or hot corrosion) are required.